Headphones are designed to produce sound waves to be presented to a listener's ear. Those sound waves are produced by a diaphragm, such as for example in a headphone cup. The diaphragm is coupled to a driver, which is responsive to an audio signal. The audio signal is produced by an audio signal source, such as an MP3 player or another entertainment device.
Ideally, the sound waves presented to the listener's ear are faithful to the original audio signal. However, the shape and size of the human ear performs a transfer function on sound waves presented to the outside of the ear. When designed, known headphones are optimized for an ear geometry that is intended to be representative of most human ears, such as for example the KEMAR standard (including the pinna, the outside part of the ear, sometimes referred to as the auricle, and the concha, the bowl-shaped part of the pinna, the latter of which generally forms a cavity for receiving sound waves). Similarly, when designed, known headphones are optimized for an expected position of the headphone with respect to that ear geometry, which is generally responsive to a relative shape of the headphone or its cushion with respect to the shape and size of the ear.
One problem in the known art is that, while designed for a standard ear geometry that is representative of most human ears, known headphones only approximate the actual ear geometry of any particular listener. Most real human ears differ at least somewhat from the standard ear geometry used for design, as a consequence of variation among the ear shapes and sizes of different people. This has the effect that the standard ear geometry will often not be a faithful representation of the listener's actual ear.
Similarly, another problem in the known art is that, while designed for a standard ear geometry that is representative of most human ears, known headphones only approximate the actual position of the headphone with respect to that ear geometry. When in actual use, most real listeners position their headphones at least somewhat differently from the standard used for design, also as a consequence of variation among the ear shapes and sizes of different people, as well as a consequence of variation in the user's choice of headphone position. This also has the effect that the position the headphones were designed for will often not be a faithful representation of the actual position used by the listener. This is also a consequence of variation among different people, their ear shapes and sizes, and the most comfortable position they might individually select for using their headphones.
The known art has the drawback that the sound waves presented to the listener can differ substantially from their ideal presentation, due to the headphones having been designed only for an expected average ear and an expected headphone position.